This invention relates to a driver circuit for an active matrix display device, and particularly a row select driver circuit for driving the pixel rows of a liquid crystal display (LCD) using thin-film transistors (TFT).
Liquid crystal display (LCD) or similar devices normally use thin-film MOS transistors deposited on a substrate, usually glass. At present, almost all commercially available active matrix liquid displays (AMLCD) are unscanned in that the scanning signal is applied external to the AMLCD.
An unscanned AMLCD requires one external lead for each column and row line. For example, a direct line interface driver for a black and white 768X1024 XGA computer display would require 1792 leads. The need for this large number of leads in the display drivers is a serious problem, which gets worse as the resolution and complexity of displays increase. Two major challenges are to reduce the number of required input leads and to "integrate" the driver circuitry onto the display substrate.
U.S. Pat. No. 5,034,735 discloses a driving apparatus using two transistors per pixel row for producing select and deselect signals and sequentially addressing them through the control gates. However, the scanning driver circuit and a signal driver circuit are adapted for a ferroelectric liquid crystal device, not for TFT-LCD.
U.S. Pat. No. 5,157,386 discloses a circuit driving an AMLCD with video digital data of K bits. An analog switch receives a video voltage and outputs the video voltage to each column when the analog is turned on by a control signal. This is not a circuit for selectively driving the rows of a display.
U.S. Pat. No. 5,113,181 discloses a display, wherein a data driver demultiplexer is used, but does not disclose a scan driver circuit.
U.S. Pat. No. 5,313,222 discloses a select driver circuit for an LCD display, which has to sustain a great deal of electrical stress.